The study found that during the course of a school year, a student may learn as much as three times more material from a top-performing teacher as a similar student does from a bottom-performing teacher. And that extra learning translates to the bottom line once the student leaves school.

In fact, in one year, a well-above-average teacher — in this case, one that’s in the 84th percentile of effectiveness — may lead to as much as $400,000 in additional lifetime earnings for her class of 20 compared to an average teacher, the NBER study said.